The proposed research has two basic objectives. First, the conformational equilibria of normal and mutant hemoglobins (Hb) will bA quantitatively characterized by a peptide tritium exchange technique. Globins to be examined initially include HbA, HbF, HbS, Hb Hammersmith, Hb Gun Hill, Hb Sabine, and Hb Zurich as well as free alpha subunits. These specific mutant globins are of interest since they are relatively rapidly proteolytically degraded in the developing red blood cell. The present research will examine the link between the conformational behavior of these mutants, their proteolytic susceptibility, and their in vivo lifetime. Such linkage has been proposed in several forms, most specifically in a "thermodynamic" control mechanism for protein degradation. This mechanism predicts direct dependence of the proteolytic rate of a protein in vivo on the equilibrium distribution of (partially) unfolded conformers of that protein. The mutant hemoglobins offer a potentially excellent system for testing this mechanism, and thereby provide direct information on catabolic pathways in the developing RBC. In conjunction with the conformational studies, proteolytic susceptibility studies of mutant globins will also be carried out. The second series of experiments will attempt to modulate the conformational equilibria of hemoglobins by chemical modification. These experiments are intended to provide a model for a possible (chemical) approach to Hb 'conformational disease'. These studies will focus primarily on the stabilization of free alpha subunits of HbA, as encountered in beta thalossemia.